This invention relates in general to electrical grounding clamps, and in particular, to a grounding clamp for use with a grounding electrode such as a pipe, conduit or ground rod.
A number of universal ground clamp devices exist for electrical ground connection with grounding electrodes of various diameters. Conventional devices provide a means to electrically connect solid copper wire such as AWG wires sizes 6-12 to a grounding electrode by a clamp device. However, the coupling of the clamp device must be maintained free from corrosion and mechanical failure at all times, both at the connection with the terminated ground wire and at the connection to the grounding electrode.
When a grounding electrode is covered with paint, rust or some such thin layer of insulating material over the base metal, procedures must be utilized for cleaning the grounding electrode""s surface to ensure a suitable grounding. While these surface preparation procedures are usually effective in assuring a properly conditioned surface for grounding, they are also time consuming and, on occasions, may be improperly utilized or not used at all.
In some ground clamps, the ground connection between the ground wire and conduit is achieved by tightening a strap around the grounding electrode. Some of such straps incorporate abrasives that penetrate any oxide layer or paint. Clamps have also been configured in which the bolt that tightens the strap bears normally directly against the grounding electrode. Although, in this arrangement, the bolt can be configured to penetrate any oxide layer or paint, the arrangement has the drawback that the bolt can undesirably penetrate or deform the grounding electrode. As a remedy, in some clamps, a plate, strap, or flap, is disposed between the bolt and grounding electrode such that the bolt bears against the plate, strap, or flap, which presses radially against the grounding electrode. However, with the disposition of the plate, strap, or flap, between the bolt and grounding electrode, good connection between the clamp and a grounding electrode having an oxide layer, paint, plating, or other thin insulating layer cannot be assured.
The present invention provides a structure which is effective to ensure a proper contact with the base metal of the grounding electrode to be grounded, even if the surface has not been properly scraped or sanded, without damaging the grounding electrode.
Briefly stated, the invention in a preferred form is a universal ground clamp for clamping a ground wire to a grounding electrode comprising an elongated flexible strap sized and shaped to be tightly wrapped and secured around the electrode with the strap having integrally formed thereon projections shaped and sized to cut into the electrode to form an intimate electrical contact, and means for tightening and securing the straps with the projections intimately engaging the surface of the electrode, wherein pressure is exerted on the portion of the strap bearing the projections in a direction normal to the electrode. In one embodiment, the means for securing the strap comprises a U-shaped bracket with a pair of legs between which ends of the strap may extend, and means projecting through the legs and strap for simultaneously securing the U-shaped bracket to the ends of the strap and to the electrode such that the projections are forced into intimate electrical contact with the electrode by normally directed pressure. The projecting means may have a wire engaging means for electrically connecting a wire to the electrode.
The invention is suitable for use with grounding electrodes of various diameters that have an oxide layer, paint, plating or other thin insulating layer. A good electrical connection is formed between the universal ground clamp and the grounding electrode without the risk of puncture or deformation damage to the grounding electrode. In one embodiment, the invention also has the installation advantages of not requiring the removal of any fasteners and only requiring access from one side. In addition, good electrical coupling is assured between the ground wire or wires and the universal ground clamp.
In a preferred embodiment, the universal ground clamp comprises an elongated strap having first and second ends. The first end of the strap has an an abrasive outer surface. The universal ground clamp further comprises a U-shaped bracket which has a first leg which has an opening that is registered with a threaded opening of a second leg. The second end of the strap has a plurality of longitudinally spaced apertures. The second end of the strap is tightly wrapped around the grounding electrode and an aperture is aligned between the opening of the first leg and the threaded opening of the second leg. The first leg may have a retaining flange projecting toward the second leg which acts as a strap guide. A bolt defining a longitudinal axis comprises a torque receiving portion and an axially extending threaded shaft threadably couplable with the threaded opening of the second leg and passable through an aperture of the second end of the strap and the opening of the first leg. An electrical coupling means connects the ground wire to the universal ground clamp. The longitudinal axis of the bolt is oriented perpendicular to the first end to permit the bolt upon application of a torque to the torque receiving portion to frictionally engage the first end substantially perpendicular thereto and thereby force the outer abrasive surface of the first end of the strap to intimately contact the grounding electrode.
In one aspect of the invention, the bolt further comprises an internally threaded head having a transverse opening. A set screw is mountable to the bolt and axially threadably displacable relative to the transverse opening. A terminated ground wire is passable through the transverse opening. Application of a torque to the set screw displaces the set screw relative to the opening, forming an electrical coupling between the universal ground clamp and the ground wire.
In another aspect of the invention, the first end of the strap is connected to the first leg of the U-shaped bracket by welding, riveting or other bonding means.
In a further aspect of the invention the first end of the strap further comprises a loop produced by folding the first end of the strap. The first end wraps around the first leg and further includes a through hole aligned between the openings of the first and second legs. The loop, set adjacent to the first leg of the bracket, the flange, and the wrapped strap maintain the relative positions of the first end and the first leg.
In yet another aspect of the invention, the second end of the strap further comprises an abrasive surface positioned to contact a substantial arcuate portion of the grounding electrode. The abrasive surfaces of the first and second ends of the strap preferably comprise a plurality of cutting edge forming holes formed through the strap.